1. Heat oven to 425 degrees F. Sift together flour, baking powder and salt into large bowl.
2. Cut in shortening with pastry blender or 2 knives used scissors fashion until incorporated.
3. Whisk together sweet potatoes and 3/4 cup milk in small bowl until blended. With a fork, gradually stir sweet potato mixture into flour mixture until blended; do not overmix. If dough is too dry, add remaining milk, 1 tablespoon at a time, until dough sticks together.
4. Place dough on floured cloth or surface. Knead 8 to 10 times. Roll or pat biscuits into 13 x 8-inch rectangle, about 1/2 inch thick. Cut out with floured 2-inch biscuit cutter or cut into 2-inch squares with knife. Gather scraps, pat out and cut. You should have 20 biscuits. Place on baking sheet.
5. Bake in 425 degree F oven for 8 to 10 minutes or until golden. Serve warm. Makes 20 biscuits.